1. Field of the Invention
The invention relates to sampling devices and to air supply systems incorporating such devices and sterile filling apparatus including such air supply systems.
2. Brief Review of the Prior Art
There are many circumstances where gas from a gas stream is flowed through a tube from a source to means utilizing the gas and where the gas may contain unwanted particulate contamination. An example of this is sterile filling apparatus such as blow/fill/seal apparatus where the gas is air and is used to prevent contamination in the sterile packaging of articles such as sterile liquids. Plainly, the presence in the air of particulate contaminants such as micro-organisms can compromise the sterility of the packaging process and may result in packaged product being contaminated.
In order to remove contamination, the air supply is normally filtered through a filter (such as HEPA or 0.2 xcexcm rated filter) having a rating sufficient to remove unwanted particulate contaminants such as micro-organisms. The filter can be inspected at the end of its life to see whether its integrity has been compromised to allow contaminants to enter the air stream supplied to the apparatus. This procedure may, however, render a large quantity of the articles unusable if it is found that the filter integrity has been compromised, since it is not possible to say when during the life of the filter the compromise occurred so making it necessary to remove all articles produced during the life of the filter.
In order to try and overcome this problem, it has been proposed to include in the tube a sampling port in the form of a pipe extending through a wall of the tube normal to the length of the tube. This port is connected to a unit containing a filter which filters out all particulate contaminants in a sample airstream taken from the port. At intervals, the port is closed and the unit removed so that any particulate contaminants on the filter material can be identified. In the case of biological materials, this may be done by culturing. If an unacceptable level of contaminants is present, the batch of articles produced with a contaminated airstream can be identified and removed.
FIG. 1 shows a sampling port of this known type inserted in a tube. Referring to FIG. 1, the tube 100 is of generally constant circular cross-section along its length and passes air from a source to apparatus utilizing the air. A sampling port 101 is inserted in the tube with the port extending normal to the axis of the tube. Air flows through the sampling port to a unit containing a filter as described above. At intervals, the port is closed and the unit removed so that any particulate contaminant on the filter material can be identified.
It is a problem with a sampling port of this known type that it does not always reliably identify the presence of particulate contaminants. There can be occasions when sampled air shows no contaminants but replacement of the filter element at the end of the filter element life shows the integrity of the filter to have been compromised so allowing contaminated air to pass to the article. It is then necessary to remove from production all the articles made during the life of the filter. This is plainly unsatisfactory.
According to a first aspect of the invention, there is provided a sampling device for sampling gas from a gas stream flowing from a source to means utilizing said gas to determine the presence of particulate contamination comprising a pipe through which the gas stream is flowed, a flow divider receiving the gas stream from the pipe and separating the gas stream into first and second flows, the first flow passing to said gas utilizing means and the second flow passing to a contamination detector for determination of particulate contaminants per unit volume present in the gas stream and comprising a deceleration volume disposed downstream of the flow divider and arranged to decelerate the second flow before the second flow exits for contamination detection.
By arranging the flows in accordance with the first aspect of the invention, a gas sample is obtained for analysis which will reveal reliably the presence of particulate contaminants.
According to a second aspect of the invention, there is provided a sampling device for sampling gas from a gas stream flowing from a source to means utilizing said gas to determine the presence of particulate contamination comprising an inlet tube through which the gas stream is flowed, a housing for receiving a portion of the gas flowing through the inlet tube, and an exit pipe for receiving another portion of the gas flowing through the inlet pipe, wherein the housing includes an outlet for connecting to a contamination sampling means and wherein the volume of the housing is such as to decelerate the portion of the gas received therein.
According to a third aspect of the invention, there is provided a sampling device for sampling gas from a gas stream flowing from a source of gas to means utilizing the gas to determine the presence of particulate contamination comprising a housing for receiving and decelerating a portion of the flow, an exit tube for conveying the remainder of the flow and a sampling tube leading from the housing for connection to contamination detection means.
According to a fourth aspect of the invention, there is provided an air supply system comprising a source of air, a filter supplied with air from said source, an outlet passage for conveying filtered air from the filter to means utilizing said air, the outlet passage including a sampling device according to the first, second or third aspects of the invention.
According to a fifth aspect of the invention, there is provided a sterile packaging apparatus for packaging articles comprising an air supply system according to the fourth aspect of the invention, the outlet passage leading to a filling and sealing station of the apparatus.
According to a sixth aspect of the invention, there is provided a method of sampling an air stream to test for the presence of particulate contaminants comprising dividing the air stream into first and second flows, decelerating the first flow, passing decelerated first flow to contamination detection means and passing the second flow for utilization.
The following is a more detailed description of some embodiments of the invention, by way of example, reference being made to the accompanying drawings in which: